Category Archives: FrontPage

Resistance to Odometry is futile

It sure is. But a good odometry in a robotic context is an objective that is hard to achieve.  For a robot like the aMoSeRo only two main velocities are relevant: linear and angular speed. Both do not occur on the same time, but still – correctly determining any of them is essential as most higher algorithms like slamming and planning highly depend on it. For me in a out of time running thesis, this task can be the biggest still kinda opened challenge.

All other system parts like gmapping, robot_pose_ekf, tf_broadcasts, sensor code, drivers, dynamic_reconfigure (insert long list of other important things here) are up and well enough running. Most of the thesis is written, only evaluation (experiments) and conclusion (the big round up in the end) is still missing.

Therefore I am really looking forward to a time after my thesis – full of well deserved sleep and a university degree 🙂

Screenshot24.09.2014

Howto run two 6V DC motors with arduino micro

So before trying to get the planned stepper motors running, I quickly put a dc motors setup together:

I’ve got two dc motors coming with my make block robot starter kit. And for research I also ordered a small l298n motor controller shield which is able to control motors up to 24Vs and 2A each by  4 small input wires at  for example 3,3V and 2 additional +5V motor enablers.

There is a nice little page which explains all states of the L298N according to the arduino micro here. For a [amazon &title=Raspberry Pi&text=Raspberry Pi] I found a nice Youtube video explaining everything here.

For me in the end both motors rotated quite nicely, like this video shows:

For the micro I wrote this peace of code:

 

Arduino Micro and ultrasonic sensor HC-SR04

This is my very first arduino application. But its simple and amazing.

You will need 4 female to female jumper wires and [amazon &title=HC-SR04&text=HC-SR04] ultrasonic sensor, a microusb cable and in the end you’ll be able to measure distances with this little device.

Just wire it like shown below:

IMG_20140513_173350

I used pins 7 (orange echo) and 8 (yellow trigger) for data pins, 5V(red) and ground(black).

I have taken some code from this page. The result you can see in the screenshot below, its a amount of cm written in the serial console:

Screenshot - 13.05.2014 - 17:37:28

 

Rasberry Pi Robot with ROS, Xtion and working base_controller teleop

Before I dismantle my little [amazon &title=Raspberry Pi&text=Raspberry Pi] Robot #1 , I wanted to have a little video of its base_controller working together with the turtlebot teleop. It uses the geometry/Twist messages to transmit moving information like a lot of ROS Robots do.

As you see there is a little acceleration control implemented which makes the robot start smoothly and stop after gently after no key is pressed anymore. In case of emergency its possible to hit e.g. the space bar for a instant full stop.

This robot isn’t very fast – but the next one will be. So this was a successful ROS-learning robot which I can recommend to everyone who wants to know how ROS Robots work.
Its a bit hard to get all of the source compiled on the small arm cpu, and there are nearly no precompiled packages – but it takes away all the fear from compiling errors in the future 🙂